I allow my garden to go wild, i.e. increase the biodiversity. That seems to keep the plant-eating critters at bay. I think what happens is that once you start a garden you provide a food source for many plant eaters, and so they come in and multiply, but there's a lag time between that and when the predators arrive and multiply. You gotta just have a little patience and wait. I remember losing a few plants in the beginning and wondering where all the ladybugs and other beneficials were; however, now, not only do I have plenty of them, but I also see a lot of their larvae, which look like little tanks. I've also seen quite a few eggs of the lacewing.
And there are some proactive steps you can take, such as adding a heavy layer of leaf mulch, which provides habitat for things like ladybugs and so many other types. And grow certain plants, such as Alyssum, which attracts parasitic wasps.
Your only other option is to keep spraying, which kills off the good and the bad, but the bad seem to somehow adapt and you need to keep changing the ingredients. And don't be fooled by the mindset some have that just because something is “natural” that it is safe. There are plenty of unsafe things in nature. I don't use anything in my garden, not even water to wash off the aphids.
But then again, I'm kind of a bug freak, so I like watching bugs at work, even some of the destructive types. Start reading up on them, and look for them as your little habitat zone becomes more diverse.
When I first started my garden I had a major infestation of slugs and snails -- they devoured all my hostas; I did nothing to combat them, but over time their numbers have greatly diminished. I think because I have attracted many predators, such as moles and other animals, such as ground beetles. I think many people automatically think of beetles as bad animals to have in the garden, but there are many beneficial beetles, not just the ladybug. Heavy mulches give them habitat.
http://www.motherearthnews.com/orga...d-beetles-helpful-garden-insects-zw0z1301zkin
http://www.pacifichorticulture.org/articles/garden-allies-predaceous-ground-beetles/
More interesting reading...
http://aggie-horticulture.tamu.edu/galveston/beneficials/beneficial-25_long-legged_flies.htm
http://www.organiclandcare.org/free-education/plants-that-attract-beneficial-insects.html
http://www.rodalesorganiclife.com/g...ould-actually-want-around-your-plants/slide/2